Because of the low weight of a kart, driver's weight plays an important role in the system. Generally, lower driver's weight is preferable. Although higher weight will produce more traction while cornering, lower weight produces less centrifugal force, allows better acceleration and braking.

Don't sacrifice proper hydration pursuing lower body weight before a race. Even slight dehydration affects attention, reaction speed and proper judgement, which can be more important to overall success than insignificantly lower weight. This can be easily tested by timing the same driver without and with a ballast weight.